Saxon blue / indigo carmine dye

[James Blanchard]

Hi all,

Some time back I picked up a lovely large Persian carpet. It has a range of blues including a light blue, and a lot of green.

Recently there was a water spill and it was wet for some time, and we noticed that there was some bleeding of the green.

I have done a bit of reading and it seems that the culprit is likely the so-called "Saxon blue", or indigo carmine. A Turkotek Salon on dyes by Pierre Galafassi (Salon 129: http://www.turkotek.com/salon_00129/salon.html) indicated that greens Saxon blue was not light fast and tended to bleed, as did greens made from the dye. Other reading indicated that it was not uncommon in Persian and Turkish rugs from about 1850 until 1910, such that it was one indicator of approximate age.

Here is a link to a more detailed scientific analysis of the indigo carmine dye, supporting Pierre's assessment. https://www.researchgate.net/publication/272310463_Indigo_car mine_Understanding_a _problematic_blue_dy e

My practical question is whether anyone has any thoughts about how to avoid dye bleed, and perhaps any suggestions about how best to clean up any spills, should they occur. It would seem to make sense to use acidic solution (like vinegar / water) if cleaning is required, since alkali solutions are known to loosen the dye from the wool.

Picture of a section of the rug is below (I don't have a picture of the dye run). Interestingly, there hasn't been that much dye fading, which one might have expected.

Any experience or information would be welcome.

James

https://c2.staticflickr.com/2/1921/44659473425_290af988 35_b.jpg

[Rich Larkin]

Hi James,

Nice rug! I can't help much with the principal question. In those situations, I usually put a detailed note in a bottle with Pierre's name and address on the outside on waterproof tape, and I fling it into the Atlantic as far as I can. Maybe he will spot your inquiry in this case.

Meanwhile, I notice that in the minor border immediately below the main border, on the left side of the third white flower in from the left, there appears to be a vertical seam where there was a very slight loss of design elements. Perhaps where a slit was repaired, or some such thing. Is that so, or is it an illusion?

In addition, is there any chance you could post a reasonable close look from the back?

Rich

[Pierre Galafassi]

Rich, your bottle-throwing skills are admirable. This one even went up the Rhine River landing in front of my house.

Hi James,
Nice rug!
You probably have identified the criminal all right: Saxon blue.

A bit of doubt remains though, which only a proper analysis could eliminate: You are puzzled by the lack of evidence for poor lightfastness. And right you are.

That leaves us with 3 possibilities:
- Either your rug passed most of its years in an obscure wine cellar (Not a bad choice, I would too)
- Or the rug was woven less than a couple of decades ago. Some very ancient synthetic dyes are still manufactured today in local 'cottage-factories' . I would not bet the house on Saxon Blue having yet disappeared from even the most remote Asian bazaars.
- Or the blue is not Saxon blue, but another ( synthetic-) dye sold on the market, created for another end-use, but misused for rugs. The most obvious candidate fitting the profile (Blue dye with rather poor wet-fastness but good light-fastness on wool) would belong to the amino-anthraquinone family which offers clear violet, blue and blue-green dyes. The family contains dyes with good light-fastness and with either low-, medium or high wet-fastnesses. Dyes of the former type (so-called migrating ‘acid’ amino-anthraquinone dyes) appeared on the market during the first decades of the XX century, some are still manufactured in pretty large volumes (a business of over 10 million $ )and used by the textile industry, for example for wall-to-wall polyamide carpeting.

Thanks for the ref. to the excellent paper authored by de Keijzer and al.
They make a note which could be of high interest for ruggies: They mention the 'corroding' properties of Saxon Blue. An occurrence already noted by some Turkotekers in the past.
Perhaps a comment could be useful here.
Saxon blue is produced by so called 'sulfonation' of indigo, a jargon which means that indigo is reacted with sulfuric acid, leading to the introduction of 'sulfonic' groups in the indigo molecule and giving it a good solubility in water (and a lousy affinity for wool, hence the poor wet-fastness).
This new molecule, once 'isolated' (purified), has no detrimental effect for the wool structure whatsoever. But, during the XVIII-XIX centuries, chemistry was still in its infancy and Saxon blue producers were not necessarily aware of the fact that the dye powder which they were selling still contained lots of impurities, one of them being residues of sulfuric acid, which of course would attack the wool fibers during the dyeing process and even after it.:sherlock:


About cleaning of traces of bleed. Sorry James, I can’t give any good advice. Except one, don’t even dream of doing any wet treatment.

Best regards
Pierre

[James Blanchard]

Hi Rich,

I think there isn't a slit... just an optical glitch, or something. I've posted some additional pictures below.

Pierre,

Thanks for the excellent information. I'd be very surprised if this is a recent rug. My guess was early 20th century, at the latest. But this is not my area of expertise. I'm going to take a closer look at the carpet to see if I detect more evidence of lack of light-fastness, etc. The bleed is very minimal, so no rescue operation is needed. However, it's good to know for future reference, and to avoid water!

James

https://c2.staticflickr.com/2/1939/45580337211_bab115e7 e6_b.jpg

https://c2.staticflickr.com/2/1937/31707939978_92d80900 37_b.jpg

https://c2.staticflickr.com/2/1933/31707939958_306fa387 b8_o.jpg

[Marvin Amstey]

As far as future spills are concerned: use lots of cold acidified water and a small shop vac to extract as much of the water as possible.... over and over again until the stain is gone. After that exercise, take it to a professional rug cleaner who also should be able to remove most of the bleeding.

[James Blanchard]

As far as future spills are concerned: use lots of cold acidified water and a small shop vac to extract as much of the water as possible.... over and over again until the stain is gone. After that exercise, take it to a professional rug cleaner who also should be able to remove most of the bleeding.

Thank you for the advice, Marvin.

James

[Rich Larkin]

Hi James,

Have you ventured into attributing your handsome rug to a particular venue? I would think, Sultanabad.

On the matter of having found a synthetic color (leaking!) in your rug, as undesirable as that is, it helps a lot if it looks good! :cheers:

Rich

[Chuck Wagner]

James,

Nice catch !

Green with jealousy ---> :D

Regards
Chuck

[James Blanchard]

Hi Rich,

I'm really not sure about the attribution. "City" carpets confound me. I have heard suggestions of "Mahal" and "Sultanabad". For me, I think it was the elegant design and ivory ground that made it stand out, despite it being well outside of my usual preference for "tribal" rugs.

James

[James Blanchard]

James,

Nice catch !

Green with jealousy ---> :D

Regards
Chuck

Thanks, Chuck.

That was almost Weileresque...

:applause:

[Rich Larkin]

Hi James,

"Mahal" usually describes a coarser grade from the Sultanabad area, though some of them are very attractive on account of good color and bold design. Anyway, you picked a beauty.

Rich

[Alain Bueno]

As I wrote before to determine the origin of a rug looking at an image is hazardous. However if you want an opinion some clues should be considered. Dealing with a Persian ( or Turkmen) piece the most important is to indicate the type of knot used. It will filters the possibilities and together with others considerations will leave the viewer with few options.
Of course I am speaking of rugs wich origin is not straightforward.